1. Field of the Invention
The invention relates to the field of crude oil production and, more specifically, to a system and method for detecting and locating a breach of a pipe in a nested multi-pipe petroleum well through the use and measurements of pressure sensors and pressure valves. The phrases “petroleum well,” “production well,” “hydrocarbon well,” and “oil well” are used synonymously throughout this application, and includes the production of petroleum in both liquid and gaseous form.
2. Background Information
A typical hydrocarbon production well is comprised of a production pipe nested within one or more casing pipes, all of which are generally concentrically aligned. These typical hydrocarbon wells emanate a natural well pressure that is different from atmospheric pressure, which well operators use, inter alia, to remove the hydrocarbon fluids and gases from within the well. This natural well pressure can be generated over a large volume of the formation, and will try to escape by the path of least resistance to the surface. Thus, the natural well pressure may naturally flow into the well pipes of the hydrocarbon well. This pressure may then be used to detect a breach between two well pipes of a nested multi-pipe production well, as described herein.
While the production pipe communicates hydrocarbons to the surface, surrounding casing pipes primarily serve to reinforce the main borehole. The casing pipes are usually cemented into place, although the annulus 26 between the production pipe and the innermost casing pipe may instead be sealed from the hydrocarbon producing zone with a packer, which is a common downhole tool used to isolate a production well annulus 26 from hydrocarbon liquids and gases.
Generally, the production pipe and casing pipes are made of steel, which is susceptible to oxidation and corrosion over time that may cause the oil well to leak hydrocarbon fluid or gases through the casing pipes and into the surrounding earth. These leaked hydrocarbons may eventually surface at ground level and, as they move through the earth, cause a harmful environmental impact to surface and underground water and soil, as well as wildlife, during migration to the surface. Such leaking might also cause an unsightly accumulation of crude oil at the surface.
Numerous United States patents address the detection of leaks within production wells. For example, U.S. Pat. No. 3,776,032 discloses a method of protecting a well from an inflow of either gas or liquid. The detection process involves the use of pressure mud pulses from a pair of acoustical transducers, which generate signals in the form of pressure waves, both before the drilling mud is circulated to the drill bit and after drilling mud is circulated through the drill bit. The difference, if any, between the two pulses is then converted to a signal and transmitted to the surface.
U.S. Pat. No. 4,114,721 discloses a pair of acoustic detectors moving through a well to detect sound indicative of a casing leak. As hydrocarbon fluids or gases move through a breach in the casing, the acoustic noise is monitored at two locations within the borehole. The signals from the monitors are transmitted to the surface and used to determine the location of the breach.
U.S. Pat. No. 4,101,827 discloses a method of detecting leaks in an underground pipe that is made of an insulator. The process involves partially filling the pipe with an electrically-conductive fluid (such as tap water), passing an electrical current through the fluid to establish a voltage gradient along the length of the fluid in the pipe, then analyzing the resulting gradient to determine the location of the leak. The voltage source is connected to a first electrode, which is immersed in the liquid at one pipe end, and to a second electrode, which is driven into the ground. This method involves inserting a wire inside the underground pipe in order to properly determine the potential drop across the gradient. The well operator determines the location of the leak by measuring the length of wire inserted into the underground pipe at the location of the potential drop—i.e., the point of minimal voltage.
U.S. Pat. No. 5,548,530 discloses a non-intrusive high-precision ultra-sonic leak detection system for pipelines used to identify development of even very minute leaks. The system locates these leaks to within several meters of their actual location in a segment of the pipeline between two site stations of the leak detection system. Leaks are located and their locations determined by their effect on the pressure of the pipeline and the effect of the pressure change on liquid density. U.S. Pat. No. 6,442,999 includes a master station to which these site stations transmit sonic wave data in order to perform calculations to determine the presence of a leak and its location.
U.S. Pat. No. 6,530,263 discloses a system for locating leaks in a pipeline using loggers that are positioned along the pipeline at spaced intervals. These loggers detect and store sound data produced within the pipeline and download the stored sound data to a computer system for analysis. The location of leaks is derived from this analysis.
U.S. Pat. No. 6,595,038 discloses an apparatus for determining the position of a leak in an underground pipe for fluid or gas using acoustic sensors. A first sensor is coupled to the pipe while a second sensor is movable above the pipe. Both sensors detect sound either carried along the walls of the pipe or along fluid in the pipe. Based on the sound reading, the location of the leak can be determined.
U.S. Pat. No. 6,668,619 discloses a method and apparatus for locating the source of a leak in a pipeline using match pattern filtering techniques. These match pattern filters discriminate against background noise and pressure disturbances generated by other, non-leak sources. This method uses acoustic signals to determine whether a leak exists and where it is located.
U.S. Pat. No. 6,650,125 discloses locating leaks of conductive fluids, such as ionized water, from non-conductive structures, such as pipes, through the use of a charge generator. The generator charges and discharges the conductive fluid, and a capacitive-type portable detector detects the variable charge that is induced in the fluid.
While the prior art discloses several complex methods for detecting breaches in piping, the current art does not disclose a method of detecting breaches in a nested multi-pipe hydrocarbon production well that is simple, inexpensive, and accurate. Furthermore, the prior art discloses methods of breach detection that require disposing tools and equipment down the wellbore, which complicates the breach-detection process. A need therefore exists for a cost-efficient and simple system and method for locating crude oil leaks in these nested multi-pipe production wells.